1. Field of the Invention
The present invention relates to a cooling apparatus for a linear motor, and more particularly to a cooling apparatus for a linear motor effectively cooling heat generated when the motor is driven and providing an accurately maintained motor characteristics.
2. Description of the Conventional Art
Linear motors having cold plates mounted on one edge of an armature are known in the art. Also, known are armatures having cooling coils or channel therein. These armatures are comprised of laminates of magnetic materials.
For example, a conventional linear motor, shown in FIGS. 1 and 2, is comprised of a xe2x80x9cUxe2x80x9d-shaped stator back plate 50 having inner surfaces thereof on which opposing permanent magnets 51, each having N- and S-poles, are sequentially disposed with alternate N- and S-poles arrangements; and a rotor 55 having a frame 54 to which a plurality of coil units 53 are provided, with a gap C between the coil units and the stator 52.
On a lower portion of the frame 54 are provided the coil units 53 having core, not shown, made of magnetic material or non-magnetic material around which plural coils are wound.
With the stator 52 and the rotor 55 being spaced apart from each other by a predetermined gap C, a thrust generated by the permanent magnets 51 and the coil units 53 makes it possible the movement of the rotor 55.
As described above, the operation of the linear motor is made by applying electric current to the coil units by a controller (not shown). When current is supplied to the coil constituting the coil units 53, magnetic field is generated from the coil and core. A thrust is then generated between magnetic field thus generated and permanent magnets 51 provided inside stator back plate 50, causing a linear motion of the rotor 55 provided to a lower portion of the frame 54. A moving speed of the rotor 55 linearly traveling along the inner side of the stator 52 and the thrust associated therewith and so forth may be controlled by the controller.
The repeated linear motion of the rotor 55 inside the stator 52 permits the production of eddy currents, currents and so forth induced in the permanent magnet 51. This generates relatively higher temperature heat between the coil units 53 and the permanent magnets 51. Heat generated between the coil units 53 and the permanent magnets 51 varies depending upon the rated currents determined by the coil diameter.
High temperature heat generated between the rotor and the stator causes magnetic characteristics of the rotor or the stator to be varied, which makes it difficult to perform a precise linear motor control. In other words, since the permanent magnet and coil units are generally made of material of lower thermal resistance, characteristics thereof are apt to vary due to heat generated between the rotor and the stator, thus resulting in different characteristics of the linear motor itself.
Therefore, it is an object of the present invention to solve the above-mentioned problems, by providing a cooling apparatus for a linear motor which effectively cools heat generated when the motor is driven and provides an accurately maintained motor characteristics.
Anther object of the present invention is to provide the cooling apparatus for the linear motor being capable of selectively cooling the motor by detecting a position of the moving linear motor to supply an air into air supply holes through a supply pipe installed at a bottom portion of a stator back plate, or to introduce an air into an air gap through supply pipes installed at both sides of the stator back plate.